OBJECTIVEThe authors sought to test the hypothesis that adding dexamethasone (DXM) to atorvastatin (ATO) potentiates the effects of ATO on chronic subdural hematoma (CSDH).METHODSSixty patients with CSDH underwent 5 weeks of treatment with an additional 7-week follow-up. Patients were randomized to receive a 5-week regimen of ATO 20 mg daily or ATO 20 mg daily plus a DXM regimen (ATO+DXM). The 5-week DXM regimen was 2.25 mg daily for 2 consecutive weeks, followed by 0.75 mg twice daily for 2 weeks and 0.75 mg once daily for 1 week. The primary endpoint was hematoma reduction assessed by neuroimaging at baseline and at 5 weeks of follow-up. Secondary outcomes included neurological improvement assessed by using the Markwalder’s Grading Scale and Glasgow Coma Scale (MGS-GCS).RESULTSThe mean patient age was 66.6 years, and 25% of patients were women. The patients who were treated with ATO+DXM had more obvious hematoma reduction at the 5th week (between-groups difference 18.37 ml; 95% CI 8.17–28.57; p = 0.0005). This reduction started from the 2nd week (14.51 ml; 95% CI 4.31–24.71; p = 0.0056) of treatment and persisted until the 12th week (17.50 ml; 95% CI 7.30–27.70; p = 0.0009). Complete recovery of neurological function (MGS-GCS grade 0) at 5 weeks was achieved in 83.33% and 32.14% of patients in the ATO+DXM and ATO groups, respectively. At the 5th week, patients receiving ATO+DXM had significantly lower levels of T cells and higher levels of regulatory T cells and endothelial progenitor cells in their peripheral blood.CONCLUSIONSATO+DXM was more effective than ATO alone in reducing hematoma and improving neurological function in patients with CSDH. These results require further confirmation in a randomized placebo-controlled trial.Clinical trial registration no.: ChiCTR-IPR-14005573 (http://www.chictr.org.cn/index.aspx)